Prism for collimation and illumination structure for window glass of vehicle

Abstract

To provide a prism for light collimation which has a high degree of freedom of assembly and can respond to space saving, and an illumination structure for a window glass of a vehicle including the prism.SOLUTION: There are provided: a prism for light collimation used in illumination of a glass for a vehicle which includes a light incident surface, a light emitting surface, an end face positioned opposite to the light incident surface relative to the light emitting surface, and a reflecting surface for reflecting the light incident from the light incident surface toward the light emitting surface, where in a cross section of the prism including the light incident surface, the reflecting surface, the light emitting surface and the end face in its contour, at least one straight part is included in the contour of the reflecting surface, and light which is incident from a predetermined position of the light incident surface and is reflected from a plurality of positions having different inclination angles to the light emitting surface of the reflecting surface emits at the same emitting angle, on the light emitting surface; and an illumination structure including the prism, a light source, and a glass plate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a collimating prism used for lighting vehicle window panes and the like, and to an illumination structure for vehicle window panes that utilizes this prism. [Background technology]

[0002] In recent years, an increasing number of automobiles and other vehicles have roofs made largely of glass. Previously, glass roofs had the problem of being susceptible to sunlight and outside temperatures, but these problems have been resolved by improving the heat-shielding and heat-insulating properties of glass. By making the roof out of glass, an open interior space can be achieved, improving passenger comfort.

[0003] In particular, battery-powered electric vehicles (BEVs) have become popular in recent years, but because many BEVs have batteries installed on the floor, the floor is higher than in conventional vehicles, reducing the clearance between the roof and the passengers' heads.Even in such cases, the use of glass roofs can avoid a feeling of claustrophobia and ensure passenger comfort, so glass roofs are expected to become even more popular in the future.

[0004] As a means of further improving the design of glass roofs and increasing their added value, attention is being paid to lighting structures that make the roof itself illuminate. However, since using special glass would inevitably increase costs, a technology is being considered in which light emitted from a separate light source is guided through an optical prism onto the ordinary window glass used in glass roofs, causing the window glass to illuminate.

[0005] For example, Patent Document 1 describes a vehicle glazing comprising a pane body assembly having an outer surface facing the vehicle surroundings and an inner surface facing the interior of the vehicle, the pane body assembly having a light-guiding layer, and a light source configured to couple light into the light-guiding layer, wherein an input coupling element is provided on the inner surface of the pane body assembly to couple the light emitted by the light source into the light-guiding layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2023-520153 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 describes that the input coupling element has a wedge-shaped or trapezoidal cross section and acts as an optical prism to optimize the input coupling angle of light coupled into the light guide layer. However, because commonly used light sources such as LEDs emit light in multiple directions, a prism with a wedge-shaped (triangular) or trapezoidal cross section cannot collimate the light entering the light guide layer (inner glass) with a constant incident angle.

[0008] Laminated glass, in which an inner glass pane and an outer glass pane are bonded together via an interlayer film, is sometimes used as window glass for automobiles. To illuminate the window glass using an external light source, it is preferable for the light to be guided to a location away from the light source by repeatedly reflecting between the inner surface of the inner glass pane (the inner surface of the window glass) and the interface between the interlayer film and the inner glass pane. In this case, the optimal angle of incidence of light onto the window glass is limited to a narrow range, so it is preferable for the prism used to introduce light emitted from an external light source into the window glass to function as a collimating prism, which adjusts the angle of incidence of light onto the window glass, and therefore the angle of emission of light from the prism, to a constant value.

[0009] On the other hand, for industrial production to match the production scale of automobiles, it is preferable that the light source and prism can be easily assembled.Furthermore, in order to ensure freedom in design of window glass, it is preferable to keep the size of accessories such as the light source and prism as small as possible.

[0010] Therefore, the present invention aims to provide an optical prism (optical collimating prism) that has a collimating function to output at least a portion of the light incident from a light source as parallel light, is easy to assemble with window glass and light sources, and can also be used to save space, and an illumination structure for vehicle window glass that is equipped with such a prism. [Means for solving the problem]

[0011] As a means for solving the above problems, the present invention includes the following configurations.

[0012] The first configuration of the present invention is A light-collimating prism for use in lighting vehicle glass, comprising: a light entrance surface and a light exit surface; a reflecting surface that reflects the light incident from the light incident surface toward the light exiting surface, In a cross section of the prism including the light incident surface, the reflecting surface, and the light exiting surface in its contour, the contour of the reflecting surface includes at least one linear portion, Light that enters from a predetermined position on the light entrance surface and is reflected from a plurality of positions on the reflecting surface that have different inclinations with respect to the light exit surface is The light is emitted at the same emission angle on the light exit surface. It is a prism.

[0013] According to the prism having the above configuration, the angle of emergence of light emitted from the exit surface is collimated, so that the light can be made to enter parallel at different positions on the vehicle glass.

[0014] The second configuration is the prism according to the first configuration, In a cross section of the prism including the light incident surface, the reflecting surface, and the light exiting surface in its outline, the reflecting surface has a polygonal line shape, The broken line is composed of three or more tangent lines that are tangent at different positions to a curve having a different radius of curvature depending on the distance from the light output surface. It is a prism.

[0015] A prism having the above configuration can function as a collimating prism for aligning the exit angle of light emitted from the light exit surface even if the position of the light source opposite the light entrance surface is shifted from the ideal position.

[0016] A third configuration is a prism according to the first or second configuration, wherein: The light incident surface is a prism, and the angle it forms with the light exit surface exceeds 90° (preferably 115° to 125°). According to the prism having the above configuration, it is possible to reduce light loss in the prism and improve the light utilization efficiency.

[0017] A fourth configuration is a prism according to any one of the first to third configurations, wherein a light guide portion having the light entrance surface, the light exit surface, and the reflecting surface; a support plate portion having a first surface flush with the light output surface and a flat second surface opposite to the first surface; Prisms having alternating structures arranged along the longitudinal direction. With the prism of the above configuration, by joining the flat second surface of the support plate portion to the substrate on which the light source (LED) is installed, multiple light sources can be placed opposite the light entrance surface of the light guide portion at exactly the same height position, thereby preventing or suppressing a decrease in brightness due to misalignment between the light source and the prism.

[0018] A fifth configuration is a prism according to any one of the first to third configurations, wherein In a plan view, the light entrance surface and a distal end of the light exit surface relative to the light entrance surface are: It is a prism with a semicircular outline. According to the prism having the above configuration, a wide range of glass can be illuminated with a small number of light sources.

[0019] A sixth configuration is a lighting structure for a vehicle window glass, a glazing body having at least one glass pane; a light source and a prism according to any one of the first to fifth configurations, the light source is disposed on the light entrance surface side of the prism, The light output surface of the prism is adhered to the surface of the glass plate via an adhesive layer to form a lighting structure. According to the lighting structure configured as described above, light emitted from the light source can be efficiently guided within the glass plate of the window glass body.

[0020] A seventh configuration is the lighting structure according to the sixth configuration, the window glass body has a three-layer structure consisting of a first glass plate, a second glass plate, and an interlayer film disposed between the first glass plate and the second glass plate; light that enters the window glass body through the adhesive layer from a plurality of positions on the light exit surface of the prism is totally reflected at the interface between the second glass sheet and the intermediate layer; It is a lighting structure. According to the lighting structure configured as above, the light emitted from the light source can be efficiently guided within the second glass layer.

[0021] An eighth aspect of the present invention is the lighting structure according to the seventh aspect, The refractive index of the material that constitutes each element of the lighting structure is The relationship between prism > adhesive > second glass plate > interlayer is met. It is a lighting structure. The lighting structure having the above configuration contributes to improving the light utilization efficiency, and also allows the prisms that make up the lighting structure to be made smaller, thereby improving the design of the illuminated glass.

[0022] A ninth configuration is an illumination structure according to any one of the sixth to eighth configurations, The window glass body is a roof glass. It is a lighting structure. [Effects of the Invention]

[0023] According to the prism of the present invention, a certain collimating function can be maintained even if the position of the light source is slightly shifted from the optimum position, so that the assembly work of the lighting structure can be simplified and high luminous efficiency can be ensured. [Brief explanation of the drawings]

[0024] [Figure 1A] 1 is a partial plan view (top view) of a prism according to one embodiment of the present invention. [Figure 1B] FIG. 2 is a cross-sectional view taken along line IB-IB in FIG. [Figure 2] 1 is a cross-sectional view showing a state in which a prism is bonded to an inner glass to form an illumination structure according to an embodiment of the present invention. [Figure 3] 1 is a schematic cross-sectional view for explaining optical designs in the illumination structures of the prior art and the present invention. [Figure 4] FIG. 1 is a schematic diagram for explaining Snell's law. [Figure 5] 1A and 1B are diagrams showing the results of an optical simulation of an illumination structure including a prism with a rectangular cross section in the prior art; [Figure 6A] FIG. 6 is a diagram showing the optical path of light that satisfies the total reflection condition at the interface of the inner glass in the simulation results shown in FIG. 5. [Figure 6B] 1A and 1B are diagrams showing the results of an optical simulation of an illumination structure including a prism with a wedge-shaped cross section in the prior art; [Figure 6C] 10A and 10B are diagrams showing the results of optical simulations of an illumination structure in a prototype of the present invention, the illumination structure including a collimating prism whose reflective surface has a curved cross-sectional profile. [Figure 7A] 1 is a diagram showing the light path within a collimating prism when a light source is in a predetermined position in an illumination structure including a collimating prism whose reflective surface is a compound plane in one embodiment of the present invention. [Figure 7B] 1 is a diagram showing the optical path within a prism when a light source is shifted from a predetermined position in an illumination structure including a collimating prism whose reflecting surface is a compound plane in one embodiment of the present invention. FIG. [Figure 7C] 10A and 10B are diagrams for explaining the angle between adjacent reflecting surfaces in a collimating prism whose reflecting surfaces are composite planes; [Figure 8]10A and 10B are diagrams illustrating the results of an optical simulation of an illumination structure including a prism whose reflective surface is a composite plane in one embodiment of the present invention. [Figure 9] FIG. 10 is a perspective view showing a model of an illumination structure used in a simulation of light guide efficiency. [Figure 10] 10 is a graph showing the change in light guide rate depending on the position of the light source when prisms of various shapes are used. [Figure 11] 4 is a graph showing the change in light guide rate depending on the position of the light source for light of different wavelengths in the lighting structure according to an embodiment of the present invention; [Figure 12A] 10 is a schematic cross-sectional view illustrating a case where the light-entering surface of the prism is inclined with respect to the light-exiting surface in the illumination structure according to one embodiment of the present invention. FIG. [Figure 12B] 10A and 10B are diagrams showing the results of an optical simulation of an illumination structure including a prism whose light entrance surface is inclined relative to its light exit surface. [Figure 13A] FIG. 10 is a partial plan view showing a state in which a light source is assembled to a prism according to a modified example of the embodiment of the present invention. [Figure 13B] FIG. 13B is a cross-sectional view taken along line XIIIB-XIIIB in FIG. 13A. [Figure 13C] FIG. 13B is a cross-sectional view taken along line XIIIC-XIIIC in FIG. 13A. [Figure 14] 1 is a schematic plan view illustrating an illumination structure including semicircular prisms in one embodiment of the present invention; [Figure 15] FIG. 15 is a cross-sectional view taken along line XV-XV in FIG. [Figure 16] FIG. 10 is a diagram showing the illumination state of the roof glass when one LED light source is placed opposite a rod-shaped prism. [Figure 17A] FIG. 10 is a diagram showing the illumination state of the roof glass when three LED light sources are placed opposite a rod-shaped prism. [Figure 17B] FIG. 10 is a diagram showing the illumination state of the roof glass when three LED light sources are placed opposite a semicircular prism. DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1A is a partial plan view of an optical prism 1 (hereinafter, sometimes referred to as prism 1) according to one embodiment of the present invention, also showing a light source (LED) 2 disposed opposite prism 1. FIG. 1B is a cross-sectional view taken along line IB-IB in FIG. 1A. In this example, prism 1 has a long, plate-like shape and is surrounded by a light incident surface 1a through which light from light source 2 enters, an end surface 1d (the end surface distal to the light incident surface) located opposite light incident surface 1a in the width direction of prism 1, a light exit surface 1b that contacts light incident surface 1a on one longitudinal side and contacts end surface 1d on the other longitudinal side, and a reflecting surface 1c that contacts light incident surface 1a on one longitudinal side and is located opposite light exit surface 1a in the thickness direction of prism 1. Light entering through light incident surface 1a is reflected by reflecting surface 1b toward light exit surface 1b. The end surface 1d is not essential, and for example, the light-emitting surface 1b and the reflecting surface 1c may be in direct contact with each other to form an end portion (edge).

[0026] The following description will be given using roof glass as a vehicle window glass, but this is not limiting. Examples of vehicle window glass include, in addition to roof glass, windshields, door glass, side glass, quarter glass, and rear glass. The light exit surface 1b of the prism 1a is flat or slightly curved to fit the shape of the roof glass (see FIG. 2) on which the prism 1 is installed. The reflecting surface 1c is shaped so that light entering from a predetermined position on the light entrance surface 1a and reflected from multiple positions on the reflecting surface 1c with different inclination angles relative to the light exit surface 1b can exit at the same exit angle on the light exit surface 1b. In the prism 1 of the present invention, in a cross section (FIG. 1B) of the prism 1 including the light entrance surface 1a, the reflecting surface 1c, the light exit surface 1b, and the end surface 1d, the outline of the reflecting surface 1c includes at least one linear portion (four linear portions S1 to S4 in the illustrated example). The outline of the light entrance surface 1a in the cross section may also be linear.

[0027] It is preferable that the inclination angle of the reflecting surface 1c relative to the light exit surface 1b first inclines in a direction away from the light exit surface 1b from the light entrance surface 1a side to the end surface 1d side, and then gradually changes in a direction approaching the light exit surface 1b.

[0028] 2 is a cross-sectional view showing an optical prism 1 and a light source (LED) 2 mounted on roof glass 10 in one embodiment of the present invention. The roof glass 10 has a laminated glass structure in which an outer glass 7 facing the outside of the vehicle cabin and an inner glass 8 facing the inside of the vehicle cabin are bonded together via an interlayer 9, and the light-emitting surface 1b of the prism 1 is bonded to the surface 8a of the inner glass 8 via an adhesive layer 11. The present invention is characterized by the shape of the prism 1, particularly the shape of its reflective surface 1c, and the prism 1, light source 2, adhesive layer 11 and roof glass 10 constitute the main components of an illumination structure for roof glass 100 of the present invention.

[0029] Figure 2 also shows a cross section of an LED board 3 on which the light source 2 is installed, a relay board 6 connected to the LED board 3 and connected to a harness 12 via a socket 6a, and a housing 4 that houses these together with the prism 1 and the light source 2 and assembles them to the roof glass 10, but these configurations can be changed as appropriate depending on the shape of the prism 1 and the roof glass 10.

[0030] FIG. 3 is a conceptual diagram illustrating the optical design of a roof glass lighting structure 100 in accordance with the prior art and the present invention. Light L emitted from the exit surface 1b of the prism 1 is refracted at the interface B1 between the prism 1 and the adhesive layer 11 and at the interface B2 between the adhesive layer 11 and the inner glass 8, and then enters the inner glass 8. In order to illuminate the roof glass 10 over a wide area, it is preferable that the light L entering the inner glass 8 be guided as far as possible while repeatedly reflecting at the interface B3 between the inner glass 8 and the interlayer 9 and at the surface 8a of the inner glass. To achieve this, the light L entering the inner glass 8 from the prism 1 via the adhesive layer 11 must be totally reflected at the interface B3 between the inner glass 8 and the interlayer 9. The conditions for this can be calculated using Snell's law.

[0031] As shown in Figure 4, the absolute refractive index n A From the medium A, the absolute refractive index n B When light enters medium B, the angle of incidence based on the normal N of the interface is θ A , the refraction angle is θB Then, from Snell's law, sinθ A / sinθ B =n B / n A This becomes: From this, the conditions under which refraction can occur in medium B are: sinθ A n A / n B =sinθ B ≦sin90°, so the incident angle θ A The critical angle θm is sinθm=n B / n A θ A When θm, light enters medium B from medium A, and θ A When θm > θm, total reflection occurs at the interface between media A and B.

[0032] From the above relationship, it is possible to determine the conditions under which light emitted from optical prism 1 in the structure shown in Fig. 3 passes through the adhesive layer, enters inner glass 8, and is totally reflected at interface B3 between inner glass 8 and interlayer 9. As an example, for light with a wavelength of 520 nm (green light), if the refractive index of optical prism 1 is (1.60), the refractive index of the adhesive layer is (1.54), the refractive index of inner glass 8 is (1.52), and the refractive index of interlayer 9 is (1.48), then the condition that must be satisfied for the angle of incidence θ1 from optical prism 1 to interface B1 between optical prism 1 and adhesive layer 11 is 68.1°<θ1<72.0°.

[0033] As described above, the preferred angle range is limited, so the optical design of the prism 1 is important in illuminating the roof glass 10. Ideally, it is desirable for light L emitted from different positions on the exit surface 1b of the prism 1 to be emitted at the same emission angle (refraction angle if there is a medium above) θ2. In this case, since light that enters from the light source 2 and travels directly toward the exit surface will have different emission angles depending on the radiation direction, it is desirable to adjust the shape of the reflecting surface 1c of the prism 1 so that light L reflected at different positions on the reflecting surface 1c is incident on the exit surface 1b at the same incident angle θ1 and is emitted at the same emission angle (refraction angle) θ2.

[0034] 5 is a schematic cross-sectional view showing an illumination structure 100 equipped with a prism 1 having a rectangular cross section, but the outer glass is not shown because it plays little role in illumination and the adhesive layer is thin (the same applies to FIGS. 6A to 6C and 8). The dashed lines in the figure indicate the optical paths of light determined by optical simulation.

[0035] 6A to 6C are schematic cross-sectional views showing illumination structure 100 equipped with prisms 1 of different shapes, and dashed lines indicate only the optical paths of light that satisfy the above-mentioned total reflection conditions as a result of optical simulation. Fig. 6A shows illumination structure 100 equipped with prism 1 having a rectangular cross section as shown in Fig. 5. As can be seen from comparing Fig. 5 and Fig. 6A, with rectangular prism 1, the light emitted from prism 1 is hardly collimated, and much of the light that passes through intermediate film 9 is scattered and lost.

[0036] 6B is a schematic cross-sectional view showing an illumination structure 100 equipped with a prism 1 having a wedge-shaped cross section, which corresponds to the illumination structure described in Patent Document 1. With this shape, the light emitted from the light source 2 cannot be collimated at different positions on the reflecting surface 1c of the prism 1, and therefore only a portion of the light reflected from the reflecting surface 1c of the prism and entering the inner glass 8 is totally reflected at the interface 9a with the interlayer 9.

[0037] FIG. 6C is a schematic cross-sectional view showing an illumination structure 100 equipped with a collimating prism 1 designed as a prototype of the present invention. In this example, the reflecting surface 1c of the prism 1 is curved, and the cross-section shows a curved outline. The radius of curvature of the outline varies depending on the distance from the light input surface 1a, which is positioned opposite the light source. By making the reflecting surface 1c curved, the inclination of the reflecting surface 1c can be changed depending on the radiation direction of light from the light source 2, making it possible to collimate the exit direction of light reflected from multiple positions on the reflecting surface 1c in approximately the same direction. Note that in the example shown, the outline shows a curve in which the radius of curvature increases with increasing distance from the light output surface, but the outline may take a different curved shape depending on the optical design of the illumination structure.

[0038] 6C, light emitted from a light source placed at a predetermined position and entering the prism is collimated in an appropriate direction by reflecting surface 1c, thereby increasing the amount of light that is totally reflected at interface B3 between inner glass 8 and interlayer 9, and allowing the light to be guided through inner glass 8 to a position away from the light source. However, in this lighting structure 100, in order for prism 1 to exhibit its collimating function, light source 2 must be accurately positioned in accordance with the optical design; if the position of light source 2 is misaligned, prism 1 will not be able to exhibit its appropriate collimating function.

[0039] As a result of continuing research to solve the above problems, it was discovered that by configuring the reflecting surface 1c of the prism 1, which is molded into a shape with a collimating function, to include at least one straight portion in the outline of the cross section including the light entrance surface 1a, the light exit surface 1b (Figure 3), and the reflecting surface 1c, it is possible to maintain the collimating function of the prism 1 and maintain the effectiveness of the lighting structure 100 even if the position of the light source 2 is shifted to some extent from the optimal position.

[0040] The outline of the reflecting surface 1c in the cross section may be composed of curved and straight lines, or may be a polygonal outline composed of multiple straight lines at different angles relative to the light incident surface 1a. In this case, the outline of the reflecting surface 1c preferably comprises three or more straight lines, more preferably five or more straight lines, and may even comprise eight or more straight lines. The shape of the polygonal lines is preferably an approximation of a curve that optimizes the collimating function. For example, the polygonal line may be composed of three or more tangent lines that are tangent at different positions to a curve whose radius of curvature varies depending on the distance from the light incident surface 1a (e.g., a curve whose radius of curvature increases with increasing distance from the light incident surface 1a). There is no particular upper limit on the number of straight lines, but it may be 12 or less from the perspective of the function of compensating for light source misalignment and ease of processing.

[0041] In the above explanation, the shape of prism 1 was described in terms of the cross-sectional outline, but if prism 1 has a longitudinal shape extending in a linear direction when viewed from above light-emitting surface 1b, reflecting surface 1c will have a shape that includes flat surfaces, for example, a shape consisting of multiple planes (composite planes) that are at different angles relative to light-entering surface 1a. On the other hand, if prism 1 is curved in plan view, the linear portion in cross section will also be a curved surface. For example, if prism 1 is arc-shaped in plan view, reflecting surface 1c will include a conical surface.

[0042] Fig. 7A is a schematic cross-sectional view showing the collimating function of a prism 1 according to the present invention, showing a case where the reflecting surface 1c of the prism is composed of a composite plane. The planes P1, P2, P3, and P4 form linear portions S1-S4 at different angles relative to the incident surface 1a in the cross-sectional outline of the prism 1, and the outline of the reflecting surface 1c is a polygonal line. Light L1-L4 incident in a predetermined direction from a light source 2 positioned opposite the prism 1 is reflected in the same direction by the multiple planes P-P4. Fig. 7B shows a case where the position of the light source 2 is shifted downward in the configuration shown in Fig. 7A. In a shape in which the outline of the reflecting surface 1c is curved, if the position of the light source 2 is shifted, the angle of the reflecting surface 1c with respect to the direction of incidence of the light L will change, and the collimating function will be lost. However, if the outline of the reflecting surface 1c includes linear portions (for example, if the reflecting surface is made of a composite plane), at least a portion of the light (L1, L3, L4 in the figure) that was reflected in a predetermined direction before the position of the light source 2 was shifted will be reflected in the same direction at a different position on the linear portions of the reflecting surface 1c (S1, S3, S4 in the figure) after the position of the light source 2 is shifted, and a certain degree of collimating function can be maintained. Note that Figures 7A and 7B are provided for illustrative purposes and do not reflect the actual dimensional ratios.

[0043] FIG. 7C is a diagram further illustrating the shape of the reflecting surface 1c of the prism 1. The reflecting surface 1c of the prism 1 has a shape that first moves away from the light-emitting surface 1b and then gradually approaches the light-emitting surface 1b. For example, if the reflecting surface 1c is a complex of n planes P1 to Pn (n is an integer greater than or equal to 3, 4 in the figure), and the outline of the reflecting surface 1c in a cross section of the prism 1 is made up of n linear segments S1 to Sn, then the linear segment adjacent to the light-entering surface 1a is S1, an arbitrary linear segment is Sk, and the linear segment adjacent to Sk (k is an integer between 1 and n-1, 3 in the figure) on the distal side of the light-entering surface 1a is Sk+1, then the angle α that S1 makes with the light-emitting surface 1b is preferably greater than 0. Furthermore, the angle βk formed by Sk and Sk+1 is preferably less than 180°. Preferably, α is 10° to 30°, and each of the βk's is independently 160° to 180°. The angular conditions described here are conditions relating to angles measured in a cross section with the shortest contour length, for example, in a cross section perpendicular to the longitudinal direction when the prism is a long, plate-like prism. Therefore, the above-described angular conditions can also be considered as angular conditions between adjacent planes. Furthermore, in terms of thickness, the prism 1 may be thickest between the light incident surface 1a and the end face (edge) of the prism facing the light incident surface. Furthermore, the position where the prism 1 is thickest is preferably the position where Sk and Sk+1 meet, and may be, for example, the position where S1 and S2 meet.

[0044] 8 is a schematic cross-sectional view showing an illumination structure 100 equipped with a prism 1 whose reflecting surface 1c is made up of five compound planes. Optical simulation was also performed on this configuration, and it was confirmed that a certain degree of collimating function can be obtained from each surface that makes up the reflecting surface 1c.

[0045] 6A, 6B, and 6C, the lighting structure 100 shown in Fig. 8, and a lighting structure 100 (not shown) equipped with a prism 1 whose reflective surface is made up of ten compound planes, were compared by optical simulation to compare the light transmission rate according to the shape of the prism 1. Fig. 9 is a perspective view showing the configuration of the model used in the simulation (for convenience of illustration, the surface 8a of the inner glass 8 is shown as the upper surface). The actual dimensions of the model were a square roof glass 10 with sides of 300 mm, to which rod-shaped prisms 1 with different cross-sectional shapes corresponding to each lighting structure were adhered. Prism 1 had a refractive index of 1.597 (refractive index for green light with a wavelength of 520 nm; the same applies below) and a maximum thickness of 3.0 mm. The adhesive layer (not shown) had a refractive index of 1.540 and a thickness of 0.05 mm. The inner and outer glass plates 8 and 7 had refractive indices of 1.519 and 2.0 mm, respectively. The intermediate film 9 had a refractive index of 1.482. The ratio of the total luminous flux to the luminous flux emitted from light source 2 was evaluated at a position 30 mm away from the end face of the prism facing the light incident surface (dashed line). Evaluations were also conducted when light source 2 was shifted 0.25 mm and 0.50 mm up and down from the predetermined position where the light conductance was maximum. The results are shown in Table 1 and Figure 10. The wavelength of light used was 520 nm, which is green light. Upward shifts of light source 2 were indicated by positive values, and downward shifts were indicated by negative values.

[0046] [Table 1]

[0047] 10, a light guide rate that is more than twice as high is obtained when using a prism 1 in which the reflective surface is a curved or compound flat surface and has a collimating function, compared to an illumination structure using a prism with a rectangular cross section or a prism 1 with a wedge-shaped cross section as described in Patent Document 1. Furthermore, when using a prism 1 having a reflective surface 1c made of a compound flat surface according to the present invention, the maximum light guide rate is slightly lower than when using a prism 1 with a curved reflective surface, which is the prototype of the present invention, but it is possible to suppress a decrease in light guide rate when the light source 2 is misaligned.

[0048] Because the refractive index of each component varies depending on the wavelength of the incident light, we performed a simulation of the light conduction rate when green light (wavelength 520 nm), blue light (wavelength 470 nm), and red light (wavelength 640 nm) were incident on the prism 1. The results are shown in Figure 11. The reflecting surface 1c is a 10-surface composite. The light conduction rate for red light is lower than that for green and blue light, and the decrease in light conduction rate due to misalignment of the light source 2 is significant. This is thought to be due to the small difference in refractive index between the inner glass 8 and the intermediate film 9 for long-wavelength light. However, since the ratio of RGB luminous flux in a typical multicolor LED is, for example, approximately 45:100:15, the impact of a low light conduction rate for red light is small, and the lighting structure of the present invention is therefore not considered to pose a practical problem when displaying color images.

[0049] In the models shown in Figures 7A to 7C and Figure 8, the light incident surface 1a of the prism 1, which faces the light source 2, is perpendicular to the light exit surface 1b of the prism. However, after examining the appropriate angle of the light incident surface 1a relative to the light exit surface 1b, it was found that the angle between the light incident surface 1a and the light exit surface 1b is preferably greater than 90°. Of the light emitted from the light source 2, light radiated upward enters the prism 1 and then directly exits from the light exit surface 1b. Therefore, even in the model shown in Figure 8, only a portion of the light is totally reflected at the interface 9a between the inner glass 8 and the interlayer 9. To increase the luminous flux collimated to an appropriate exit angle among the light emitted from the prism 1, it is preferable to tilt the light incident surface 1a and guide as much luminous flux as possible to the reflecting surface 1c, as shown in Figure 12A. The angle between the light incident surface 1a and the light exit surface 1b is preferably 115° to 125°.

[0050] For a prism 1 in which the reflecting surface 1c is a composite plane, an optical simulation was performed to determine the light guiding rate relative to the inclination angle when the light incident surface 1a is inclined, as shown in FIG. 12B. If a plane perpendicular to the light exit surface 1b is taken as a reference plane R, the inclination angle φ of the light entrance surface 1a with respect to the reference plane R is preferably about 25 to 35°, more preferably 28 to 33°, and even more preferably around 30°. The inclination angle φ+90° is the angle that the light entrance surface 1a forms with the light exit surface 1b.

[0051] In the lighting structure 100 of the present invention, it is preferable that the refractive indexes of the materials constituting each element of the lighting structure 100 satisfy the relationship of prism 1 > adhesive 11 > inner glass (second glass plate) 8 > intermediate film 9. In other words, it is preferable that the refractive index of adhesive 11 is smaller than that of prism 1, the refractive index of inner glass 8 is smaller than that of adhesive 11, and the refractive index of intermediate film 9 is smaller than that of inner glass 8. This improves the light utilization efficiency and also contributes to the miniaturization of the prism.

[0052] Therefore, the materials of the prism 1 and adhesive 11 are appropriately selected depending on the material of the roof glass 10 to be illuminated.

[0053] The first glass sheet 11 and the second glass sheet 12 constituting the roof glass 10 may be made of inorganic glass or organic glass. Examples of inorganic glass that can be used include soda-lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, and quartz glass.

[0054] The intermediate film 9 may be made of, for example, a thermoplastic resin, and examples of the thermoplastic resin that can be used include polyvinyl butyral (PVB) and ethylene vinyl acetate copolymer (EVA).

[0055] The roof glass 10 may be provided with a diffuse reflection pattern. The diffuse reflection pattern may be formed in layers and is also called a scattering layer. The shape of the pattern is not particularly limited, but for example, a plurality of circular patterns may be provided at predetermined intervals. The diffuse reflection pattern may be provided on the outer glass sheet 7 (first glass sheet 11), the inner glass sheet 8 (second glass sheet 12), the interlayer film, or a member other than these. The diffuse reflection pattern may be formed by any method, such as roughening the surface of the glass sheet, printing a scattering paint on the glass surface or the interlayer film surface, or enclosing a sheet-like member printed with a scattering paint inside the interlayer film.

[0056] For the reasons mentioned above, it is preferable to use a material having a higher refractive index than the inner glass for the prism 1. For example, polycarbonate or methacrylic styrene copolymer may be used.

[0057] The adhesive layer 11 may be made of a resin having an appropriate refractive index selected from commercially available optical clear resins.

[0058] As an example of a combination, if the roof glass 10 includes polyvinyl butyral as the interlayer 9 and soda-lime glass as the outer glass 7 and inner glass 8, the prism 1 may be made of polycarbonate. In this case, the adhesive layer 11 should be made of an optically transparent resin that has a refractive index lower than that of polycarbonate and higher than that of soda-lime glass. The same applies when the roof glass 10 includes only one glass plate (for example, soda-lime glass).

[0059] The inner and outer glass may each have a thickness of about 1.0 to 6.0 mm, and the interlayer 13 may have a thickness of about 0.1 to 1.2 mm.

[0060] In the lighting structure 100 illustrated in FIG. 9, a rod-shaped (or long plate-shaped) prism 1 is bonded to the surface 8a of the inner glass near the edge of the roof glass 10. When the prism 1 is attached to a flat roof glass 10, the prism 1 may extend in a straight line, or the light-emitting surface 1b may be slightly curved to match the shape of the roof glass 10. The prism 1 illustrated in FIG. 9 is a simulation model, and the lighting structure 100 of the present invention can also be applied to large-area roof glass, for example, that occupies most of the roof of an automobile. The size of the prism 1 is not particularly limited, but the width of the light-emitting surface 1b may be approximately 10 to 30 mm and the maximum thickness may be approximately 2 to 4 mm. The length of the prism 1 may be, for example, approximately 50 to 1,000 mm. When LEDs are placed opposite the rod-shaped prism 1 as the light source 2, the LEDs may be arranged at intervals of approximately 1.5 to 50 mm, and the number of LEDs may be equal to the length of the prism 1.

[0061] FIG. 13A is a top view showing a prism 1 according to a modified example of the embodiment described above, to which a light source (LED) 2 and an LED substrate are attached. FIG. 13B shows a cross-sectional view taken along line XIIIB-XIIIB in FIG. 13A, and FIG. 13C shows a cross-sectional view taken along line XIIIC-XIIIC in FIG. 13A. In this example, the elongated plate-like prism 1 has a shape in which light guide portions G and support plate portions (plate-like support portions) F are alternately arranged in the longitudinal direction. As shown in FIG. 13C, the light guide portion G has a light incident surface 1a, an end surface 1d, a light exit surface 1b, and a reflecting surface 1c, and the limiting conditions for its cross-sectional structure are the same as those for the prism 1 described above. 13B, the support plate F has a first surface 1f that is flush with the light output surface 1b of the light guide G and a flat second surface 1g that faces the first surface, and is arranged adjacent to the light guide G along the longitudinal direction of the prism 1. It is preferable that a plurality of light guides G and a plurality of support plate members F are arranged alternately along the longitudinal direction of the prism.

[0062] The light guide G and the support plate F are integrally molded, and the thickness of the thickest part of the light guide G is equal to or less than the thickness of the support plate F. In other words, in the example shown, the prism 1 is shaped like a long plate of constant thickness, with the light guide G built in at predetermined intervals. By joining the flat second surface of the support plate G to the LED substrate 3, the height position of the light source installed on the LED substrate 3 can be accurately controlled.

[0063] 13A to 13C, the light guide G has a hexagonal shape in plan view, like a trapezoid with a rectangle joined to the apex. The dimensions of the trapezoid in the longitudinal direction of the prism 1 increase from dimension D1 at the apex close to the light source 2 to dimension D2 at the end face 1d farther from the light source 2. This allows for efficient use of light emitted from the light source 2. Correspondingly, the support plate F sandwiched between the two light guides G has a hexagonal shape in plan view, like a trapezoid with a rectangle joined to the base. The width W1 of the light guide G is smaller than the width W2 of the support plate F. The longitudinal ends of the prism 1 may have a shape similar to that obtained by cutting the light guide G or the support plate F described above.

[0064] 13A to 13C show only one embodiment of a prism 1 including a light guide G and a support plate F, and various modifications are possible depending on the design of the prism installation location or the needs of prism formation. For example, while FIG. 13B shows a configuration in which the support plate F has a first surface 1f and a second surface 1g that are parallel to each other, the second surface 1g may be inclined with respect to the first surface. Furthermore, the shape of the boundary between the light guide G and the support plate F may be different from that shown by the dashed line in FIG. 13A.

[0065] Furthermore, the prism may have a shape other than a rod shape. In order to increase the degree of freedom in the interior design of a vehicle, it is preferable that the prisms constituting the lighting structure 100 be made smaller, and in order to save energy, it is preferable to provide efficient lighting with as few light sources 2 as possible. As a result of examining the design of the lighting structure 100 from these perspectives, it was found that effective lighting can be achieved with a small number of light sources 2 by using prisms having an outline that is approximately semicircular (more precisely, approximately semicircular annular or fan-shaped) in a planar view.

[0066] FIG. 14 is a plan view showing the prism 1 attached to the inner glass 8, and FIG. 15 is a cross-sectional view taken along line XV-XV in FIG. 14. In this prism 1, the outline of the reflecting surface 1c (light-emitting surface 51b) in plan view is formed by connecting two arcs with a straight line, with the inner arc forming the outline of the light-entering surface 1a and the outer arc forming the outline of the distal end 1e relative to the light-entering surface 1a. The cross-sectional structure of this prism may also be similar to that of the embodiment described above. In the example shown in FIGS. 14 and 15, the reflecting surface 1c has a polygonal outline composed of five surfaces P1 to P5, each of which has a different angle relative to the light-entering surface 1a. However, in this case, the reflecting surface is not a composite plane, but rather a composite of curved surfaces, each of which is part of a cone with a different apex angle. 15, the light entrance surface 1a of the prism 1 is perpendicular to the light exit surface 1b, so it has a shape that forms part of a cylinder, but the light entrance surface 1a of this prism 1 may also be inclined with respect to the perpendicular plane, so that it has a curved shape that forms part of a cone. By using a prism 1 with the above shape, it is possible to illuminate a wide range of glass with a small number of light sources 2.

[0067] The main configurations of the prism 1 and the illumination structure 100 of the present invention have been described above, but additions and modifications can be made to these configurations as appropriate. For example, in the above description, the roof glass 10 is described as having a three-layer structure consisting of the outer glass 7, the inner glass 8, and the interlayer 9, but the interlayer 9 may have a two-layer structure, with one of the layers being provided with an optical pattern that enhances the visibility of reflected light. The interlayer 9 may also include other layers, such as an electrochromic layer (not shown). Furthermore, the roof glass 10 may not have a laminated glass structure, but may instead be configured to include only one glass plate (for example, the inner glass 8 for convenience).

[0068] The prism 1 is adhered near the edge of the roof glass 10, but for example, for a roof glass 10 having an approximately rectangular outline, it may be positioned near one side selected from the four sides, near two opposite or adjacent sides, near three sides, or near all four sides.

[0069] In the configuration of the illumination structure 100 shown in FIGS. 14 and 15, the contour of the distal end face 1e of the prism 1 relative to the light incident face 1a is described as an arc, but the contour may also be a part of an ellipse.

[0070] A full-color LED or a white LED may be used as the light source 2. In the above description, a plurality of LEDs are arranged along the light incident surface 1a of the prism 1, but a long LED may also be used as the light source 2. In some cases, a light guide such as a side-emitting optical fiber may be arranged along the light incident surface 1a of the prism 1, and light from a laser light source may be incident on this light guide to serve as the light source 2. [Example]

[0071] [Example 1] A simulated roof glass 10 was prepared using a laminated glass panel consisting of two 500mm x 200mm, 2mm-thick soda lime glass sheets sandwiched between interlayer films. The interlayer film 11 had a scattering layer with circular scattering patterns, each 7mm in diameter, spaced 18mm apart. The lighting unit, configured as shown in Figure 1, was placed on the short side of the glass panel and assembled as shown in Figure 2. A rod-shaped prism (maximum thickness 3mm, light output surface width 20mm, length 100mm) with six composite flat reflective surfaces was injection molded. The light output surface 1b of the prism was bonded to the glass surface with an optically transparent resin. A full-color LED was placed opposite the light input surface 1a of the prism, and illumination was confirmed. Green and blue light were emitted from the entire surface, similar to the optical simulation results shown in Figure 16.

[0072] [Example 2] To verify the effectiveness of the lighting structure 100 equipped with a prism 1 having a semicircular profile, two sheets of laminated glass with an area of ​​300 × 300 mm were prepared. The laminated structure was the same as in Example 1, but the scattering layer of the interlayer had circular patterns with a diameter of 7 mm spaced at intervals of 18 mm. A 150 mm long rod-shaped prism (same cross-sectional shape as in Example 1) was bonded to one side of the laminated glass with optically transparent resin, and three full-color LEDs were placed opposite it at intervals of 50 mm. A prism with a 10 mm radius on the light-entering surface 1a, a 30 mm radius on the distal end 1e relative to the light-entering surface, a maximum thickness of 3 mm, and five reflective surfaces was bonded to the other side with optically transparent resin, and three full-color LEDs were placed opposite the light-entering surface. The materials of each element were the same as in Example 1. When a rod-shaped prism 1 shorter than one side of the glass is used, a blind spot occurs in the illuminated area, as shown in Figure 17A, whereas when a semicircular prism 1 is used, it becomes possible to illuminate the entire surface with three LEDs, as shown in Figure 17B. [Explanation of symbols]

[0073] 1 Prism 1a Light incident surface 1b Idemitsu surface 1c reflective surface 1d end face 1e Distal end relative to the light entrance surface 1f front page 1g second side 2 light source 3 LED boards 4 cases 6 Relay board 7 Outer glass (first glass pane) 8 Inner glass (second glass pane) 9 Interlayer 10 Optical unit 11 Adhesive layer 12 Harness 10 Roof glass 100 lighting structures G Light guide section F Support plate part

Claims

1. A light-collimating prism for use in lighting vehicle glass, comprising: a light entrance surface and a light exit surface; a reflecting surface that reflects the light incident from the light incident surface toward the light exiting surface, In a cross section of the prism including the light incident surface, the reflecting surface, and the light exiting surface in its contour, the contour of the reflecting surface includes at least one linear portion, Light that enters from a predetermined position on the light entrance surface and is reflected from a plurality of positions on the reflecting surface that have different inclinations with respect to the light exit surface is The light is emitted at the same emission angle on the light exit surface. prism.

2. 2. The prism according to claim 1, In a cross section of the prism including the light incident surface, the reflecting surface, and the light exiting surface in its outline, the reflecting surface has a polygonal line shape, The broken line is composed of three or more tangent lines that are tangent at different positions to a curve having a different radius of curvature depending on the distance from the light output surface. prism.

3. 3. The prism according to claim 2, A prism wherein the light entrance surface forms an angle of more than 90° with respect to the light exit surface.

4. 2. The prism according to claim 1, a light guide portion having the light entrance surface, the light exit surface, and the reflecting surface; a support plate portion having a first surface flush with the light output surface and a flat second surface opposite to the first surface; A prism having alternating structures along its length.

5. 2. The prism according to claim 1, In a plan view, the light entrance surface and a distal end of the light exit surface relative to the light entrance surface are: A prism with a semicircular outline.

6. A lighting structure for a vehicle window glass, comprising: a glazing body having at least one glass pane; A light source and a prism according to any one of claims 1 to 5, the light source is disposed on the light entrance surface side of the prism, The light output surface of the prism is bonded to the surface of the glass plate via an adhesive layer.

7. 7. The lighting structure of claim 6, the window glass body has a three-layer structure consisting of a first glass plate, a second glass plate, and an interlayer film disposed between the first glass plate and the second glass plate; light that enters the window glass body through the adhesive layer from a plurality of positions on the light exit surface of the prism is totally reflected at the interface between the second glass sheet and the intermediate layer; lighting structure.

8. 8. The lighting structure of claim 7, The refractive index of the material that constitutes each element of the lighting structure is The relationship is prism > adhesive > second glass plate > interlayer film. lighting structure.

9. 7. The lighting structure of claim 6, The window glass body is a roof glass. lighting structure.

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